Electric switch



C. A. SCHAEFER ELECTRIC SWITCH Filed Nov. 2, 1936 July 5, 1938.

INVENTOR. 5c%aefrn ATTORNEY.

Carl fif BY 4& 48

Patented July 5, 1938 UNITED STATES ELECTRIC SWITCH Carl A. Schaefer, Detroit, Mich, assignor to Square D Company, Detroit, Micln, a corporation of Michigan Application November 2, 1936, Serial No. 108,764 g Claims.

This invention relates to electric switches automatically operable in response to an external condition.

One object of the present invention is to pro- 5 vide an improved form of electric switch operating with a snap action in response to external pressure variations.

Another object of the invention is to provide an improved form of high pressure cutout switch used in conjunction with a normal pressure responsive switch but having individual contacts.

Other objects and features of the invention will be readily apparent to those skilled in the art from the following specification and appended drawing illustrating certain preferred embodiments of the invention in which:

Figure l is a front elevational'view of a switch assembly according to the present invention with the front cover removed and parts broken away to show internal parts.

Figure 2 is a horizontal sectional view on the line II1I of Figure 1.

Figure 3 is a diagrammatic view showing the control system.v

The normal pressure responsive mechanism shown in Figure 1 is more fully described and claimed in applicant's co-pending application, Serial No. 77,723, filed May 4, 1936 for Electric switches. This switch embodies an insulating enclosure l for the switching mechanism and an operating means comprising a normal pressure responsive assembly generally indicated at 4 and the switch is provided with a further protective device comprising a high pressure responsive cutout indicated generally at 5. Within the enclosure I is mounted a conducting bracket 6 having a pair of arms 1 and 8 pivotally mounted thereon by means of the trunnion ends of studs l0 threaded into the upstanding walls of. the bracket. These arms thus rotate about the same pivotal axis and are disposed as shown in generally parallel relation and connected together with a lost motion connection by the headed movable contact surface described hereinafter. The arm 8 is a conducting arm carrying a contact surface 9 thereon at the forward side of the magnetic arm 1, which contact surface is headed or otherwise restricted in its movement with respect to the arm 1. A stationary magnet II is provided for attracting the arm 1. A stationary contact 12 is mounted on a resilient arm 13 and a cam 14 is provided for adjusting the position of the stationary contact 12 and hence the air gap between the magnetic arm 1 and the permanent magnet I II. A light tension spring 15 biases the conduct-' ing arm 8 toward engaged position. For moving the contacts to the disengaged position a pin it is rigidly mounted on the arm 1 and is adapted to be engaged by an insulating portion l1 on a lever I 8 pivoted to a fixed part. A compression spring 19 biases the lever 18 downwardly and is provided with an adjusting screw 2! for adjusting the range of operation of the device. The normal pressure responsive unit comprises a chamber 22 having a bellows 23 therein. A pin 24 is connected to the bellows and is adapted to press against the under side of the lever 18. A spring 25 is adapted to be adjusted by a knurled nut 26 which may be provided for varying the limits of the range variation of the device.

The high pressure cutout unit according to the present invention comprises a separate and distinct switching mechanism actuated upon the attainment of a predetermined maximum pressure to open its contacts. This switch comprises an enclosure 21 having connected to the bottom thereof a bellows chamber 28 within which is disposed an expansible bellows 29 having connected thereto a pin 3| for actuating the switching member. About the pin 3| is disposed a compression spring 32 opposing movement of the pin and adjustable by means of a threaded cylinder 33 through which the pin 3| projects. Within the chamber 21 is disposed an insulating block 30 on which are disposed spaced contacts electrically connected to the terminals 34 and 35. The base 30 is supported on a metallic bracket 36 and within this bracket is hingedly mounted a link 31 having arms 38 at either side of its opposite end and a centrally disposed bearing point 39. An adjusting member 4| is threaded into the enclosure 21 and is provided with a similar bearing point 42. A compression spring 43 is provided with bearing seats 44 at its ends which receive the bearing points 39 and 42. The link 31 and the spring 43 thus comprise an over center toggle adjustable through the member 4|. A pair of tension springs 45 bias the arms 38 to a fixed part of the enclosure. Upon the link 31 as by means of the knife-edged pivots 40 is mounted a contact member 46 including an insulating portion 41 carrying a contact plate adapted to bridge the stationary contacts on the base 33. A pair of light tension springs 48 are mounted at the contact side of the knife-edged mounting of the contact arm 46 and have their opposite ends connected to fixed points on the enclosure. An adjustable stop 49 is positioned to engage the contact arm 46 at the side opposite the contact carrying portion thereto.

A stationary stop 5| is provided for limiting the downward movement of the link 31. lThe pin Ii is provided with a pointed end received within a cooperating groove in the link 51.

The operation of the normally responsive pressure switch is as follows:

The parts as shown in Figure 1 are in the closed circuit position. Upon a decrease in pressure within the bellows chamber 22 the lever I! will move downwardly under the bias of the spring I. whereupon the insulating portion i1 will engage with the pin IS on the lever l and rotate this arm in a clockwise direction until it engages with the conducting arm 5 whereupon the arms I and I move together and move the contact surface 5 which is rigid with the arm 5 into its disengaged position. Similarly, when the pressure within the bellows chamber 22 increases while the contacts are maintained in the oil position the lever l8 will be moved upwardly, thus permitting the contacts to be moved into engaged position under the bias of the spring i5. Due to the rapidly increasing force of the magnet II as the contacts move toward engagement the meeting of the contact surfaces will concur with a snap action under the influence of the permanent magnet ll. Movement of the cam surface l4 will move the stationary contact relative to the magnet and by varying the air gap will vary the differential of pressure to which the switch operates. The compression spring I! is adjustable to vary the range of operation of the device. The spring 25 is adjustable to raise or lower the limits of the range of operation of the device.

The operation of the high pressure cutout mechanism is as follows:

The parts as shown in Figure 1 are in the closed circuit position. Upon the attainment of a predetermined maximum condition within the bellows chamber 25 the pin 3| will be moved upwardly and by its engagement with the link 31 will move this link and contact arm 36 in an upward direction. When the toggle formed by the spring 43 and the link 31 approaches its dead center position the force necessary to move it will rapidly decrease so that the movement thereof will occur quickly. At this time the contact lever 45 will engage the stop 45 and cause rotation of the contact lever about its knife-edge support to move the bridging contact plate to disengaged position. Upon decrease in pressure within the bellows chamber 25 the parts will automatically reverse themselves and move to bridging engagement with the stationary contacts. In the'opening operation, it is to be noted that contact pressure is maintained until the contact lever sharply engages the adjustable stop 49 whereupon the lever is rapidly rotated about its knife-edge mounting. The springs 45 are not absolutely essential to the operation of the device but without them the contact opening action is apt to be rather sluggish since at the instant of operation the force necessary to move the link 31 and the contact lever upwardly is increased by the increased tension in the springs 48. With the springs 45 the increased force of springs 48 forms only a very small part of the force to be overcome so that they will not slow up the action of the toggle in effecting quick break of the contacts. Adjustment of the cylinder 33 will adjust the pressure to which the device will operate to open the contacts. Adjustment; of the member 4i .will adjust the tension on the toggle link spring 43 and will adjust the differential between the p essure at which the contacts will be open and that at which they will be closed.

Figure 3 illustrates diagrammatically a system employing the pressure switch assembly which has previously been described. This comprises a motor 52 which may constitute a refrigerator compressor motor, or any other electrical translating device adapted to be connected to a line through a contactor 55 having a magnet coil 54 for effecting closing of the contact. In addition to the normal pressure switch 55 and the high pressure cutout 55 a manual three point switch 5'! having terminals 58 and 59 and a movable switching arm 5| is provided. With the switching arm placed in a neutral position as shown in Figure 3 the control circuit through the coil 54 will be manually opened and the translating device will remain disconnected frciua the line. Upon movement of the switching arm 6| into engagement with the terminal 59 the control circuit through the coil 54 will be closed with both the normal pressure switch 55 and the high pressure cutout 58 in series with the coil. This is the normal automatic operating connection for the circuit as it is seen that with this connection if the pressures within the bellows chambers 28 and 22 are at certain values both the controlling contacts will be closed and the circuit will be completed through the coil 54 thus connecting the motor to the line through the contactor 53. Upon a suitable decrease in pressure in the normal pressure switch 55 its contacts will be opened, thus opening the control circuit, whereupon the contactor 53 will open and disconnect the motor from the line. This is the normal automatic operation of the device wherein the motor is connected to and disconnected from the line in response to variations in p1. assure within the bellows 22. Upon the attainment of a predetermined maximum pressure within the bellows 28 the high pressure cutout 55 will operate to open its contacts, thus opening the control circuit to disconnect the motor, regardless of the condition of the normal pressure switch and these contacts will remain open until the pressure within the bellows chamber 25 decreases. In many instances it is desired to connect the motor or other translating device to the line for continuous operation independent of the normal pressure switch but maintaining the protection ailorded by the high pressure cutout. This is accomplished by moving the switching arm 5| into engagement with the terminal 55 whereupon the coil 54 will be connected in the control circuit in series with the high pressure cutout 55 only and the switch 55 will be is to be given its broadest possible interpretation,

within the terms of the following claims.

What is claimed is:

1. A pressure switchcomprising an element movable in one direction in response to a pressure condition, adjustable spring means for opposing such movement, a pivoted member movable in response to movement of said element. means biasing said member in a direction to oppose movement thereof by said element, a contact arm pivoted on said member, means biasing said arm to contacts engaged position, over-center spring means connected to said member and causing its movement to be snap-like in action, and a stop engaging said arm when said member is moved by said element to cause rotation of the arm against its biasing means to a contacts disengaged position.

'2. A pressure switch comprising an element movable in response to a pressure condition, spring means opposing such movement and adjustable to vary the range of operation of the switch, a pivoted member in the path of said element, over-center spring means connected to said member and adjustable to vary the differential or operation of said switch, a contact arm pivoted on said member, biasing means for said arm at the contact side of its pivotal mounting, and a stop engaging said arm at the opposite side of its pivotal mounting to. cause rotation of said arm against said biasing means to contacts disengaged position in response to movement of said member by said element.

3. A pressure switch comprising an element movable in response to a pressure condition, spring means opposing such movement and adjustable to vary the range of operation of the switch, a pivoted member operatively connected to'said element, a compression spring interconmeeting said member and a relatively fixed part and movable through its dead center position.

during movement of said member to extreme positions, said compression spring being adjustable to vary the differential of operation of the switch, spring means opposing moving of said member by said element, a contact arm pivoted on said member, spring means biasing said arm at the contact side of its pivotal mounting, and a stop engageable with said arm at the opposite side of its pivotal mounting to effect rotation thereof to its contacts disengaged position.

4. A pressure switch comprising, an element movable in response to a pressure condition, spring means opposing such movement and adjustable to vary the range or operation or the switch, a pivoted member operatively connected to said element, a compression spring interconnecting said member and a relatively fixed part and movable through its dead center position during movement of said member to extreme positions, said spring being adjustable to vary the difierential of operation of the switch, spring means opposing moving of said member bysaid element, a contact arm pivoted on said member, spring means biasing said arm at the contact side of its pivotal mounting, and a stop engageable with said arm at the opposite side of its pivotal mounting to efiect rotation thereof to its contacts disengaged position, the spring means biasing said member and said arm being suflicient to overcome the bias of said compression spring when in the contacts disengaged position so as to eflect return of said member and engagement of the contacts when the element is moved by the first mentioned spring means in response to a reduction in the pressure condition.

5. A pressure switch comprising an element movable in response to a pressure condition, spring means opposing such movement and adjustable to vary the range of operation of the switch, a pivoted member, a compression spring disposed between the free end of said member and a relatively fixed part and movable through dead center position during movement of said member by said element, said compression spring being adjustable to vary the differential of operation of the switch, a contact controlling arm pivoted on said member, biasing means for said arm at one side of its pivotal mounting, and a stop engaging the opposite side of said arm during movement of said member by said element to efi'ect rotation of said arm against said biasing means to actuate the switch contacts.

\ CARL A. SCHAEFER. 

